Aquatic ecology and Biodiversity

Unit 8- Animal associations and interactions

8.4. Symbiosis
Symbiosis is a partnership between two dissimilar organisms for mutual benefit. The term symbiosis applied to the close association of two distinct organisms for mutual benefit, so that each partner loses at least some degree of physiological independence. Association of this type where in which the relationship is intimate is called “physiological symbiosis” While the loose associations between animals referred to as “cleaning symbiosis”

Cleaning symbiosis
It is a mutually beneficial relationship in which certain animals remove ectoparasits, bacteria, diseased and injured tissues and unwanted food particles from other co-operating animals. This relationship is mutually beneficial. Cleaning symbiosis is of wide occurrence in the marine environment and many fishes, turtles, sea urchins are known to be cleaned by specific symbionts like fishes, shrimps and crab. Examples- Oxyjulis - a California fish is known to remove parasitic copepods and isopods from fishes. The neon goby (Elacatinus occanops) striped yellow fish found in corals, attaches to the host fish and nibbles the parasites from it. (Epinephelus sp. Serranus sp. Pomacerentrus sp.)
All cleaners are small and have fewer competitors with larger forms of food. Most of the cleaner are strips in the tropical waters for food entirely. Host has brilliant colours to attract their clients – cleaners. Cleaner adopted with long snout.
Physiological symbiosis

It is in true symbiosis. Association between the two organisms is so intimate that one of the partners may be incapable of living alone. Eg. An association between algae (Zooxanthellae ) and marine invertebrate corals
In true symbiotic associations, these unicellular algae are found within the tissue cells but in outer border line, the algal cells are found either in the body cavity or in the intracellular space. Among the marine invertebrates algal symbionts are most common in protozoan’s, sponges, coelenterates, turbillarians and molluscs.
Symbiotic relationship between algae and corals
The association is beneficial to both organisms. Here algae benefit by deriving protection and securing carbon dioxide and nitrogen’s waste products from the coral-host. While the host obtains additional oxygen supply and secured the elimination of waste substances. Symbiosis with algae is well known in Mollusca – Tridacna sp and Hippolpus sp. Tridacna is a giant mollusc inhabits in coral reefs, it grows one and half meters and it contains millions of tiny zooxanthelle on outer tissues. The symbionts remove waste products i.e., CO₂, nitrogen, phosphorus and other nutrients. Besides clam get nourishment by digesting their algae for nourishment .
Significances of physiological symbiosis are

• Both associates are benefitted
• Removal of waste from the host
• Utilisation of nutrients & wastes by algae
• Additional supply of wastes by algae
  
• Many animals obtain nutrition in corals

Symbiotic relationships are divided into two categories viz. mutualism and commensalism. In mutualism both the partners are mutually benefited while in commensalism only one of the partners is benefited.